As demands of customers have been changed due to digitalization and high-performance of electronic products, marketplace demands are also changed to the development of power supply devices which are thin and light in weight and have a high capacity with high energy density.
To meet the demand of the consumers, a power supply device having high energy density and a high capacity, such as a lithium-ion rechargeable battery, a lithium-ion polymer battery, a super capacitor (electric double layer capacitor), and a Pseudo capacitor, has been developed.
Recently, the demand for mobile electronic devices such as mobile phones, notebook computers, and digital cameras has been consistently increased, and particularly, flexible mobile electronic devices, to which a wraparound display, a flexible electronic paper (e-paper), a flexible liquid crystal display (flexible-LCD), and a flexible organic light emitting diode (flexible-OLED) are applied, have increasingly attracted the attention. Therefore, a power supply device used for the flexible mobile electronic device needs to have flexibility.
As one of the power supply devices capable of exhibiting flexibility, the development is being conducted on flexible batteries.
A nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, a lithium-ion battery, and the like, which have flexibility, may be exemplified as the flexible battery. In particular, the lithium-ion battery has high utilization because the lithium-ion battery has energy density per unit weight and may be quickly charged in comparison with other batteries such as a lead storage battery, the nickel-cadmium battery, the nickel-hydrogen battery, and a nickel-zinc battery.
The lithium ion battery uses a liquid electrolyte, and a welded metallic can is mainly used as a container. However, because a shape of a cylindrical lithium ion battery, which uses the metallic can as a container, is fixed, there are problems in that design of the electric product is restricted, and it is difficult to reduce a volume of the electric product.
In particular, because the mobile electronic device has been developed to be thin, small in size, and flexible as described above, there is a problem in that the existing lithium-ion battery using the metallic can or the battery having an angled structure may not be easily applied to the aforementioned mobile electronic device.
Therefore, to solve the aforementioned structural problems, recently, a pouch type battery, in which an electrolyte is put into a pouch including two electrodes and a separator and the pouch is sealed, has been developed.
The pouch type battery has advantages in that the pouch type battery may be manufactured in various shapes and may implement high energy density per mass because the pouch type battery is made of a flexible material.
That is, as illustrated in FIGS. 1(a) and 1(b), the pouch type battery 1 is provided to have a shape in which an electrode assembly 20 is encapsulated in an exterior material 10, and the exterior material 10 has a structure in which an inner resin layer, a metallic layer, and an outer resin layer are stacked. Among the layers, the metallic layer is an essential constituent element of the exterior material for the purpose of damp proofing, and serves to prevent moisture from permeating into an interior of the exterior material from an exterior of the exterior material because the metallic layer has high density such that the moisture and the electrolyte cannot penetrate the metallic layer, and the metallic layer also serves to prevent the electrolyte positioned in the exterior material from leaking to the outside of the exterior material.
However, there are problems in that it is difficult to ensure flexibility at a predetermined level or higher because the metallic layer has insufficient elastic restoring force, and a crack is formed in the flexible battery to which the exterior material is applied.
Further, in some instances, the pouch type battery 1 is implemented in a flexible form, and then applied to a product. However, because the pouch type battery 1 in the related art is implemented in a simple flexible form, the exterior material and the electrode assembly are damaged due to repetitive contraction and extension when the pouch type battery 1 is repeatedly bent while in use, or performance is significantly reduced in comparison with an initial design value, such that there is a limitation in exhibiting a function of a battery.